1. Field of the Invention
The present invention relates to an animal feed additive composition. More specifically, the present invention relates to a powdery or granulate ruminant feed additive composition which is stable in a rumen of a ruminant and releases lysine in the abomasum and lower digestive organs thereof, as well as to a powdery or uniformly granulate aquacultural animal feed additive composition which is stable in fresh water or seawater and releases lysine in digestive organs of aquacultural animals.
2. Description of the Background
When biologically active substances such as amino acids, vitamins and the like are orally administered directly to ruminants such as cow, sheep and the like, most of these substances are decomposed by microorganisms in the rumen, and are, therefore, not utilized effectively. Accordingly, rumen by-pass preparations for use in ruminants in which these biologically active substances are protected from decomposition by microorganisms in the rumen but are digested and absorbed in the abomasum and lower digestive organs are important in the field of ruminant feed, nutrients and chemicals.
When biologically active substances such as amino acids, vitamins and the like are added to the formula feed used in the cultivation of aqua-animals and the mixture is administered to cultivated aqua-animals, most of the biologically active substances are eluted into the water and diluted therein owing to the water-solubility thereof, and these are, therefore, not utilized effectively. Accordingly, a feed additive composition for feeding aquacultural animals which protects these biologically active substances from the elution into water but allows digestion and absorption in the digestive organs of aquacultural animals is important in the field of feed, nutrients, chemicals and the like for aquacultural animals.
With respect to ruminant feed additives containing a biologically active substance, methods are known in which a biologically active substance is dispersed in a matrix formed of a hydrophobic substance such as fats and oils or a protective substance, such as a basic high-molecular substance, and the dispersion is granulated, or where a core containing a biologically active substance is coated with a hydrophobic substance such as fats and oils or an acid-sensitive substance, such as a basic high-molecular substance.
However, in the method where the biologically active substance is dispersed into the protective substance, the biologically active substance is present near the surfaces of the particles. Accordingly, when the active substance must be well-protected, the content of the biologically active substance must be significantly decreased. Since the residence time of the water-soluble biologically active substance in the rumen is between 10-odd hours and several days, the biologically active substance cannot be protected sufficiently.
Further, a method where the biologically active substance-containing core is coated with the acid-sensitive high-molecular substance or the hydrophobic protective substance has been also proposed. However, in view of production techniques which have been used in recent years, mechanical granulation and/or coating destruction occurs due to mixing or pulverization with another feed composition. As a result, the stability in the rumen is impaired in many cases. Therefore, this composition is not desirable as a multi-purpose feed additive composition.
Thus, it is advisable that a feed additive which can withstand mixing or pulverization with another feed composition be in the form of a powder or uniform granules and prevent release of a biologically active substance in the rumen and allow elution of the biologically active substance in the abomasum and lower digestive organs.
On the other hand, with respect to feed additives for aquacultural animals which contain a biologically active substance, a method in which a core containing a biologically active substance is coated with hydrophobic substances such as fats and oils has been proposed. Regarding a method in which a biologically active substance is coated with a hydrophobic protective substance, for example, Japanese Laid-Open (Kokai) No. 173,060/1992 proposes an aquacultural animal feed starting material in which a water-soluble amino acid and/or water-soluble amino acid derivatives are coated with animal fats or waxes which are solid at room temperature, as well as a process for producing the same.
However, the method of coating a core containing a biologically active substance with a hydrophobic protective material causes, in view of the production techniques used in recent years, mechanical destruction of granules and/or coating due to mixing or pulverization with other formula feed starting materials, thereby impairing the protection in water in many cases. Thus, this composition is not useful as a multipurpose feed additive composition. In addition, the administration of coated particles alone is problematic in that it is not appropriate for cultivated aqua-animals and the necessary amount of the feed cannot be consumed.
Thus, it is advisable that a feed additive which can withstand mixing or pulverization with another aquacultural animal feed composition be in the form of a powder or uniform granules and prevent release of a biologically active substance in water and allow elution of the biologically active substance in the digestive organs of aquacultural animals. However, when lysine is used to improve nutrition of the feed, the only known lysine-containing composition which takes the form of a powder or uniform granules and which is insoluble in neutral water and is soluble in the acid of digestive organs is phosphorus wolframate.
As a substance having such desirable properties, the present inventors have found a phosphoric acid/lysine/magnesium composite salt (hereinafter referred to as the "composite salt") represented by the following formula (1), which is composed of lysine, magnesium, phosphoric acid (or phosphate) and, optionally, water. EQU R.sub.a Mg.sub.b H.sub.c PO.sub.4.(H.sub.2 O).sub.n (1)
where
R represents a lysine cation, PA1 a is between 0.15 and 1.0, PA1 b is between 1.0 and 1.42, PA1 c is between 0 and 0.3, PA1 a+(2.times.b)+c=3, and PA1 n is between 0 and 10. PA1 R represents a lysine cation, PA1 a is between 0.15 and 1.0, PA1 b is between 1.0 and 1.42, PA1 c is between 0 and 0.3, PA1 a+(2.times.b)+c=3, and PA1 n is between 0 and 10.
Four processes are known for producing this salt. These processes are described in EP 0 744 396 A1, incorporated herein by reference in its entirety.
In the first process, a secondary phosphate of magnesium is dispersed into a large amount of a basic aqueous solution of lysine, and the dispersion is heated.
In the second process, a magnesium neutral salt and phosphoric acid are mixed at a molar ratio of 1.0 to 1.45:1.0 in a large amount of a basic aqueous solution of lysine.
In the third process, a primary phosphate solution of lysine is mixed with from 1.0 to 1.45 mols of magnesium hydroxide or magnesium oxide.
In the fourth process, a solution obtained by mixing and neutralizing a basic aqueous solution of lysine with phosphoric acid at a molar ratio of 0.05 to 0.9:1.0 is mixed with from 1.0 to 1.45 mols of magnesium hydroxide or magnesium oxide.
The desired composite salt can be isolated and purifed by subjecting the magnesium salt obtained by these process to appropriate solid-liquid separation to remove excess lysine through washing. However, when the salt is actually made by one of these processes, the reaction solution solidifies or gels, or microfine crystals form, making the stirring and/or the solid-liquid separation extremely difficult.
In order to isolate the desired composite salt from such a reaction mixture which is solidified or gelled, a method is employed in which the stirring can be conducted upon diluting the product with a large amount of water or the solid-liquid separation can be conducted by milling the solid mass in a large amount of water. The production can be conducted on a small scale by this method. However, the use of a special equipment is required for production on an industrial scale, which is undesirable.
Further, when microfine crystals are formed, the solid-liquid separation takes considerable time. Therefore, in production on an industrially large scale, a large-sized separator or a large number of separators are required, increasing the cost for the separation equipment. Accordingly, this method is uneconomical. Further, in the solid-liquid separation from the reaction solution having poor slurry properties, the crystals separated tend to contain a mother liquor, which reduces the purity of the crystals.
The above-mentioned four processes for producing the composite salt are suitable for the production on a small scale, but require much improvement for production on an industrial scale.